feat: encrypted secrets vault across CLI, desktop, dashboard, and backend

Local vault (apps/cli): clean-room PRMVLT01 format — Argon2id →
XChaCha20-Poly1305, AEAD-bound header, atomic writes. vault:* / secrets:*
/ inject (primora:// refs) / agent credential broker (dummy tokens in the
child, real secret on the wire) / TTL sessions / stack:* operator group.

Project vault (backend): core.project_secrets, AES-256-GCM via the
platform encryptor. Metadata-only list, audit-logged reveal, and
secret://NAME refs resolved at job delivery — refs stored, values never.

Surfaces: dashboard Vault page (+ local-vault card under the Tauri
shell), desktop vault window via IPC to the primora binary,
secrets:* --remote CLI mode, metadata/write-only MCP tools so agents
consume secrets via secret:// refs without holding plaintext.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/database/db/models.go

@@ -307,6 +307,17 @@ type CoreProjectMember struct {
 	CreatedAt pgtype.Timestamptz `json:"created_at"`
 }
 
+type CoreProjectSecret struct {
+	ID         uuid.UUID          `json:"id"`
+	ProjectID  uuid.UUID          `json:"project_id"`
+	Name       string             `json:"name"`
+	Ciphertext []byte             `json:"ciphertext"`
+	Url        string             `json:"url"`
+	Notes      string             `json:"notes"`
+	CreatedAt  pgtype.Timestamptz `json:"created_at"`
+	UpdatedAt  pgtype.Timestamptz `json:"updated_at"`
+}
+
 type CoreScheduledJob struct {
 	ID              uuid.UUID          `json:"id"`
 	ProjectID       uuid.UUID          `json:"project_id"`